No setting has to be settled before it runs: what the request leaves open (the stock or fund, the
    history, the entry and exit levels, the costs) runs with sensible defaults, which the result names in
    one short line; a change is a new run. `question` titles its report. The call waits for the run while it
    is likely to finish inside it, then answers with the result; the run's card in the chat shows the result
    or, for a longer run, how far it is, and fills in by itself, with the next steps as choices. A run
    started here needs no `show_report_card`.

    Every account runs it within a daily allowance; a refused call does not count, and get_started and
    every run's answer give today's count.

    A run takes about 30 seconds to 3 minutes. The call returns
    `{task_id, status, kind, dashboard_url}` at once.
    `get_backtest_progress(task_id)` reports progress; when the run has
    finished, its answer carries `result`: the summary in words and, for
    a run of a year or longer, a few rounded figures (the run's return
    next to simply holding the same stock over the same dates, Sharpe,
    worst drop, trades), and `report_url`, the full report.

    `list_indicators()` lists the indicators, their settings and the
    columns each one computes. An indicator is written
    `{"id": "rsi", "params": {"length": 14}}`.

    Args:
        ticker: Stock or ETF symbol (uppercase).
        entry_indicator / entry_conditions: The entry signal (required).
        exit_indicator / exit_conditions: Optional.
        confirmation_indicator / confirmation_conditions: Optional, a filter that
            must also hold on the day the entry fires. The common use is a trend
            filter: Larry Connors' two-day RSI pullback buys only while the close is
            above its 200-day average, written as confirmation_indicator
            {"id": "sma", "params": {"length": 200}} and confirmation_conditions
            [{"column": "close", "operator": ">", "value": "SMA_200"}].
        timeframe: '1d' (daily bars, the only timeframe this connector runs).
        duration: The history tested, a span back from today: '60d', '6m',
            '1y', '2y', '3y', '5y', '10y' or 'max' (the whole history held, up to 30 years).
            There is no start date: 'since 2010' is '10y' or 'max', and the
            figures carry the years the run covered.
        direction: 'long' | 'short' | 'both'.
        position_sizing: 'fixed' | 'percent_equity' (the default, as in
            the QuanterLab UI).
        risk_per_trade: Share of the account each trade uses. 1.0, the
            default, is the whole account, as in the QuanterLab UI; a
            smaller share leaves the rest in cash and scales the result
            down with it. Sizing across several positions (Kelly, GARCH,
            fixed) is handled in QuanterLab's portfolio and paper-trading
            tools.
        stop_loss_pct / take_profit_pct / max_holding_days: Optional exits.
        spread_bps / commission_per_trade: Trading costs (default a 10
            basis point spread and no commission).
        oos_pct: Share of the history held back, 0-100 (default 0). The
            run tests only the earlier part, and its result and report say
            the held-back part was never tested; the same run again with
            `oos_pct` 0 tests the whole history.

    Conditions are lists of `{"column": ..., "operator": ..., "value": ...}`;
    every condition in a list has to hold.
        operator: ">", ">=", "<", "<=", "==", "!=", "crosses_above" or
            "crosses_below".
        column: a column the strategy's indicators compute, as
            `list_indicators()` names it ("RSI_14"; "MACD_12_26_9",
            "MACDh_12_26_9" and "MACDs_12_26_9" for the MACD line,
            histogram and signal line), or a price field ("close").
        value: a number, or another column the strategy computes
            (SMA_50 against SMA_200 needs an sma of each length among
            the strategy's indicators).
    Entry and exit usually mirror each other: RSI below 30 in, above 70
    out; MACD crossing above 0 in, crossing below 0 out. An exit identical
    to its entry closes on the entry bar or never, and the run makes no
    trades. A golden cross is entry_indicator sma 50 and exit_indicator
    sma 200, with entry SMA_50 crosses_above SMA_200 and exit SMA_50
    crosses_below SMA_200; a 200-day trend rule is sma 200 in both lanes,
    with close crosses_above SMA_200 in and crosses_below out.

    Example, long-only MACD momentum on PLTR over three years:

        start_backtest(
            ticker="PLTR",
            entry_indicator={"id": "macd",
                             "params": {"fast": 12, "slow": 26, "signal": 9}},
            entry_conditions=[{"column": "MACD_12_26_9",
                               "operator": "crosses_above",
                               "value": 0}],
            exit_indicator={"id": "macd",
                            "params": {"fast": 12, "slow": 26, "signal": 9}},
            exit_conditions=[{"column": "MACD_12_26_9",
                              "operator": "crosses_below",
                              "value": 0}],
            timeframe="1d", duration="3y", direction="long",
        )

    question: Optional. One sentence restating what the run should answer
        ("does the 2-day RSI pullback beat holding SPY?"), not the person's
        message: the title of the report the finished run becomes, and kept
        only as that.

    `report_url` is the run written up as a QuanterLab report (the answer
    against simply holding the stock and SPY, the charts, the numbers,
    what the test cannot tell), and the run's card shows its link, which
    opens without a login. A run can also be kept in the user's library with
    `save_workflow_result` (the result) and `save_trading_config` (the
    settings), when the user wants to keep it.